The present invention generally relates to the treatment of polluted water and more specifically to apparatus and methods for containment and/or equalization of overflow water and runoff in a receiving body of water.
Flexible wall tanks contained within a body of water have been used as one manner of collecting and temporarily storing overflow, urban runoff and excess storm water flow. Examples of this type of apparatus are disclosed in U.S. Pat. Nos. 4,298,471 and 4,377,477 both issued to Dunkers. In these patents Dunkers discloses a tank formed by flexible walls extending from the surface to the bottom of a receiving body of water. The tank is divided into a series of compartments by intermediate walls. Apertures in the intermediate walls allow flow from compartment to compartment, with a first or inlet compartment receiving the polluted water inflow and a last compartment connecting with the surrounding body of water. This arrangement of sequentially connected compartments provides for progressive dilution of polluted inlet water before pollutants flow into the surrounding body of water.
The tank design disclosed by Dunkers, however, will allow leakage between the flexible outside walls of each compartment and the receiving body of water since a perfect seal cannot be maintained between the weighted lower edges of the compartment walls and the bottom or floor of the receiving body of water. This leakage allows insufficiently diluted, polluted water to pass underneath the outside walls of the various compartments and into the receiving body of water before the water has reached the final compartment. Although Dunker states that minor leakage is unimportant, public concern and environmental regulation now dictate that all such leakage must be considered important.
Flexible wall tanks have generally used weighted material integrated into the lower edges of the compartment walls or, alternatively, a series of weights attached along the lower edges of the compartment walls. In either case water is able to escape from the compartment underneath the compartment walls and into either an adjoining compartment which is not the next compartment in the dilution process or directly into the receiving body of water. In this regard, the weighted material which is integrated into the lower edge of a wall is not flexible enough to provide an adequate seal around debris such as rocks and other large objects on the bottom surface or floor of the receiving body of water. On the other hand, when a series of separate weights are attached along the lower edges of the compartment walls, water can escape beneath the lower edge of a wall at locations between adjacent weights.